This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. We started a new project, in collaboration with the Gary Blissard group at BTI Cornell, to investigate the role of the transmembrane (TM) domain of GP64 for viral membrane fusion. GP64 is the major glycoprotein in autographa californica multicapsid nucleopolyhedrovirus (AcMNPV). Blissard and his coworkers found that mutants of GP64 in which the TM domain of GP64 was substituted with corresponding TM domains from six viral envelope proteins and two cellular membrane proteins could all induce hemifusion, but only some of the mutants could complete fusion activities. To examine what is the contribution of changes in the membrane structure to the differences in the fusion activities mediated by these proteins, the spin labeling method will be used to study the dynamic structures of plasma membrane vesicles (PMV) derived from sf9 cells in which GP64 and its mutants are expressed.